A phase change memory is a resistance change type memory which has phase change films, such as chalcogenide semiconductor membrane, as a memory element. The phase change film can take reversibly the stable two phase of the amorphous (amorphous) state of high resistance, and a crystalline substance (crystalline) state of low resistance according to the heat application based on a current pulse. Therefore, by a phase change memory, memory of binary information is possible by the state of a phase.
As information on prior art documents relevant to invention of this application, some are following.    [Patent Reference 1] Japanese Unexamined Patent Publication No. 2004-185755    [Patent Reference 2] Japanese Unexamined Patent Publication No. 2004-363586    [Patent Reference 3] Japanese Unexamined Patent Publication No. 2005-71500    [Patent Reference 4] International Patent Publication No. W 2003-021693    [Nonpatent Literature 1] S. J. Ahn et al. and “Highly Manufacturable High Density Phase Change Memory of 64 Mb and Beyond” IEDM 2004, pp. 907-910